Hi folks,
I substituted a series / parallel combination (2 in series with 1 in parallel) of 100v 47uF bi-polar capacitors from CPC, part number CA01894.
The combination capacitance was ~70uF near enough for our purpose.
It worked fine for about 5 months on a 16 year old incubator. During a routine service of the incubator, the capacitor combination was checked, revealing a slight swelling to the single capacitor.
Investigation and more research indicated that the capacitors could not cope with the ripple current (capacitor maximum rated as 250mA) the motor current through the capacitor combination was measured at 480mA.
The brain, using the capacitive reactance formulae, summised that twice as much current (320mA) was passing through the single capacitor than the series combination (160mA) and stressing the case, hence the swelling.
The jury is still out on whether the capacitor would have eventually burst.
I hope this helps any budding designers.
Pete
